This application claims the priority of German patent document 199 29 116.0, filed Jun. 24, 1999, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a golf club with a striking face for striking golf balls. Furthermore, the present invention relates to a method of coating a golf club, at least in the region of the striking face, by a thermal spraying method.
WO 97/20961 discloses the coating of striking faces of golf clubs after previous texturing by flame spraying or by plasma spraying. The coating may consist of metal-bonded carbides (cermets) or oxides (ceramic compounds). The coating in this publication is characterized as hard, of homogenous construction, wear-resistant, and provided with a rough surface. In coatings produced in this way, however, crack formations may occur, which limits the useful life or the lifespan of the coated striking face.
U.S. Pat. No. 5,272,802 describes a design modification of conventional golf clubs, in which thermal spraying is mentioned as a method of incorporating weight elements on the back of the golf club. The weight elements merely vary the moment of inertia of the golf club. A thermally sprayed functional coating of a striking face is not described.
The object of the present invention is therefore to provide a golf club and a method of making the golf club which enable the useful life of the coatings on striking faces of golf clubs to be increased.
This object is achieved according to the present invention in that the golf club, in the region of the striking face, at least partly comprises a coating that is either designed to be neutral in terms of stress or has compressive stresses.
It has been found that the prior art coatings for striking faces of golf clubs have inherent tensile stresses, which have an adverse effect on the period of use and the useful life. According to the present invention, inherent tensile stresses are therefore avoided in the coating of the striking face. On the contrary, stress neutrality or preferably compressive stresses in the coating are proposed. Compressive stresses mean that the cohesion of the particles in the coating is improved and the material does not tend to form cracks quickly during alternating loading.
Coatings which are neutral in terms of stress or coatings with compressive stresses can be produced by the coating being applied by a thermal spraying method with average spray-particle velocities of over 500 m/s.